Retinal pigment epithelial cells release a chemoattractant for astrocytes.

Astrocyte migration was studied using a modified Boyden chamber. Astrocytes migrated in response to a concentration gradient (chemotaxis) of retinal pigment epithelial cell-conditioned medium. In contrast, smooth muscle cell- and corneal fibroblast-conditioned media stimulated random migration (chemokinesis) of astrocytes but not chemotaxis. Furthermore, retinal pigment epithelial cell-conditioned medium stimulates only random migration of smooth muscle cells and corneal fibroblasts. The chemotactic factor produced by retinal pigment epithelial cells appears to have a molecular weight between 10,000 and 30,000 determined by ultrafiltration. Activity is lost after boiling but is stable, with a pH between 2 and 7. These results suggest that in proliferative vitreoretinopathy, retinal pigment epithelial cells on the retina and within the vitreous cavity may release a chemoattractant that stimulates astrocytes to migrate into the vitreous cavity.